PROJECT DESCRIPTION
BACKGROUND
The worldwide demand for nickel (Ni) is experiencing an unprecedented growth under current industrial and economic pressures. The European Innovation Partnership (EIP) classified Ni as a raw material with high economic importance. However, mine production mainly takes place outside of the European Union, whose mine output (in New Caledonia, Greece, Spain and Finland) represents only 8.6% of total world production.
Nickel-rich soils, such as ultramafic or serpentine soils (unattractive for agriculture in terms of fertility and productivity) are abandoned by local farmers, but have a high potential for metal recovery with application in metallurgical processes. Technologies are lacking to exploit primary sources (such as ultramafic soils) in which Ni is present at significant levels (1 500-4 000 mg kg-1), but where its extraction by conventional mining processes is not economically viable.
New means of metal extraction, recovery or recycling are therefore urgently needed to reduce the dependence of the EU on imports from metal-producing countries. Phytomining or agromining is a non-destructive approach with good potential for the recovery of high-value metals (e.g. Ni) from sub-economic ores.
OBJECTIVES
LIFE - AGROMINE aimed to demonstrate a non-destructive phytomining approach for the recovery of high-value metals (e.g. Ni) from sub-economic ores. The project’s approach would use plants to accumulate trace metals from soils and transport them to their shoots, which can then be harvested. Phytomining or agromining therefore would offer an eco-efficient alternative to classical pyro- or hydro-metallurgical processes.
The project would be in line with the circular economy concept and creates a new business aimed at recovering high-value metals, ensuring the use of secondary resources that can then be reused in other production processes.
Specific project objectives were:
- The provision of ecosystem services through agro-ecological phytomining cropping systems;
- The recovery and recycling of valuable metals from Ni-rich soils and industrial wastes (e.g. from steel industry, Ni refining, automotive and aeronautic industries);
- The use of by-products generated through the metal recovery process to improve soil fertility;
- The environmental viability of nickel phytomining (assessed through Life Cycle Assessments (LCAs), energy balance, monitoring of greenhouse gas emissions and carbon storage, and via the monitoring of the invasiveness of serpentinophyte plants and impacts on local biodiversity);
- The socio-economic viability of phytomining (assessed through the realisation of cost analyses of the phytomining chain);
- Improvements in soil quality and function, and carbon storage, after implementing phytomining cropping systems, in conformity with the Soil Thematic Strategy (COM(2012) 46); and
- The conservation of rare and endangered metallophyte species after their introduction into cropping systems through the constitution of germplasm banks and the careful use of native and adapted wild species to agricultural and land remediation sites.
RESULTS
The LIFE-AGROMINE project demonstrated the feasibility of obtaining nickel-rich products from hyperaccumulator plants on a pilot scale and integrating the different steps of the extraction process into a circular economy system.
The project identified several suitable hyperaccumulator plants naturally present in Albania, Austria, Greece and Spain and established a seed bank that allows plants to be traced. The beneficiary started to grow three key species that were identified (Odontarrhena chalcidica, Bornmuellera emarginata and Bornmuellera tymphaea) in a greenhouse in Nancy. These plants produced quality seeds for larger scale planting after the end of the project.
The project team also identified the amendment composition best suited to enhance nickel uptake – pig and chicken manure – using a range of substrates, such as ultramafic, serpentines, mine tailings and industrial waste-derived technosols. They also assessed the feasibility of recovering energy from hyperaccumulator biomass that must be incinerated to obtain ashes from which nickel can be extracted. Finally, they assessed the most appropriate nickel compounds for commercialisation and the possibility of using by-products as soil fertilisers.
From 2016 to 2021, between 0.5 and 2 tonnes of hyperaccumulator biomass were imported annually from the project sites (mostly in Albania, but also Austria, Greece and Spain) to a lab at the Lorraine University, France. This biomass was then burned in a boiler that comprised a heat reclamation system. Although the biomass had merely an average calorific value, it covered a significant amount of the heating needs of the lab during winter months (outside lockdown periods). The project recovered around 100kg of ashes from the burned biomass from which 12-15 kg of nickel was extracted. (While potassium was determined to be the best by-product, its re-use is not cost effective.)
The project’s communication campaign was curtailed by pandemic restrictions, while the initiative aimed at farmers in Greece and a symposium on agromining were cancelled. Nevertheless, the project generated interest among farmers in Greece and Albania, for whom cultivating hyperaccumulator plants on ultramafic and serpentine soils unfit for conventional farming represents a valuable alternative. The steel industry in France also expressed interest since research has shown that the toxicity level of nickel-rich sludges can be reduced by using substrates on which hyperaccumulators are planted and harvested. Such a process also significantly reduces disposal costs. The French crystal industry would also benefit from using nickel produced by agromining. AB Econick was established to commercialise the project’s findings. Although agromining cannot compete with conventional mining processes, the project demonstrated that it represents a valuable non-destructive alternative with a strong potential for the recovery of high-value metals such as nickel from sub-economic ores, on which extraction by conventional mining processes is not economically viable.
